An electronic expansion valve, as an important component for constituting a refrigeration system, is widely used in a large refrigeration unit, a large cold storage, a supermarket freezer and so on. A working process of the electronic expansion valve is generally as follows. An opening degree of a valve stem is adjusted with energizing or de-energizing of a motor, thus the flow rate of a refrigerant is adjusted.
A common electronic expansion valve includes a valve seat and a valve stem. Typically, the valve seat is provided with a valve port and two connection ports. The two connection ports may be communicated through the valve port. The valve stem has a sealing surface which is capable of fitting against an end surface, at the valve port, of the valve seat to seal the valve port. The valve stem is located in a valve cavity of the valve seat. Driven by the motor, the valve stem is axially movable along the valve cavity to open or close the valve port, so as to communicate or cut off the two connection ports.
Normally, a connection port in communication with the valve port may generate an axially upward acting force on the sealing surface of the valve stem. To avoid leakage at the valve port due to untight sealing, the valve stem may be provided with an axial through hole to allow an upper end and a lower end of the valve stem to be in the same pressure zone which generates an axially downward acting force on the upper end of the valve stem to balance forces received by the valve stem, thereby ensuring tightness. However, the upper end of the valve stem has a pressure receiving area greater than that of the lower end of the valve stem. As a result of the above, the valve stem is subjected to an axially downward acting force, which affects adversely valve opening capability of the electronic expansion valve.
In view of this, it is a technical issue to be addressed by the person skilled in the art to improve the structure of the electronic expansion valve, which ensures not only valve port tightness but also valve opening capability.